Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1479978

[PATCH v4 6/9] arm64: alternative: Add support for patching adrp instructions

Show all headers | View raw

adrp uses PC-relative address offset to a page (of 4K size) of
a symbol. If it appears in an alternative code patched in, we
should adjust the offset to reflect the address where it will
be run from. This patch adds support for fixing the offset
for adrp instructions.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 arch/arm64/kernel/alternative.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index 992918d..06d650f 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -58,6 +58,8 @@ static bool branch_insn_requires_update(struct alt_instr *alt, unsigned long pc)
 	BUG();
 }
 
+#define align_down(x, a)	((unsigned long)(x) & ~(((unsigned long)(a)) - 1))
+
 static u32 get_alt_insn(struct alt_instr *alt, u32 *insnptr, u32 *altinsnptr)
 {
 	u32 insn;
@@ -79,6 +81,19 @@ static u32 get_alt_insn(struct alt_instr *alt, u32 *insnptr, u32 *altinsnptr)
 			offset = target - (unsigned long)insnptr;
 			insn = aarch64_set_branch_offset(insn, offset);
 		}
+	} else if (aarch64_insn_is_adrp(insn)) {
+		s32 orig_offset, new_offset;
+		unsigned long target;
+
+		/*
+		 * If we're replacing an adrp instruction, which uses PC-relative
+		 * immediate addressing, adjust the offset to reflect the new
+		 * PC. adrp operates on 4K aligned addresses.
+		 */
+		orig_offset  = aarch64_insn_adrp_get_offset(insn);
+		target = align_down(altinsnptr, SZ_4K) + orig_offset;
+		new_offset = target - align_down(insnptr, SZ_4K);
+		insn = aarch64_insn_adrp_set_offset(insn, new_offset);
 	} else if (aarch64_insn_uses_literal(insn)) {
 		/*
 		 * Disallow patching unhandled instructions using PC relative
-- 
2.7.4

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v4 0/9] arm64: Work around for mismatched cache line size Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 7/9] arm64: Introduce raw_{d,i}cache_line_size Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 4/9] arm64: alternative: Disallow patching instructions using literals Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 6/9] arm64: alternative: Add support for patching adrp instructions Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 1/9] arm64: Set the safe value for L1 icache policy Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 8/9] arm64: Refactor sysinstr exception handling Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 2/9] arm64: Use consistent naming for errata handling Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 9/9] arm64: Work around systems with mismatched cache line sizes Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 3/9] arm64: Rearrange CPU errata workaround checks Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200
  [PATCH v4 5/9] arm64: insn: Add helpers for adrp offsets Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-09-09 15:10 +0200

csiph-web